Here is what the scoring site says:
http://www.mytoeflsuccess.com/computer- ... coring.htm
I'm sure you have read it and showed it to the students but it doesn't always make much sense to them without actually seeing it put to use.
If you get the students to write the required time on an overhead sheet or on something that all the students can see at once, you can mark the essay and show the students what is good and what needs improvement.
I found that giving students an essay that is written by a native speaker makes the students very depressed because they think they can never write like that. You have to start where they are and build them up gradually. (It makes some students so depressed they just memorize up to 50 essays and then write the one on the closest topic word for word for the exam. The examiners can tell these are copied.)
Take into account the things that bring down their scores as much as what is required for a 6. If the testers say that not having enough variety in vocabulary brings their score down, then it follows that they need to work on their thesaurus to have a variety of vocabulary.
Using the essays of the best students in the class gives the students a closer model to follow and will take them up slowly to what is necessary.
There is a trick to planning the timing of the writing as well and you need to teach that too by giving them plenty of practice and showing them how to budget their time for planning, writing, reviewing, and checking. We made up an acronym for checking - can't remember what it was but it was check your capitals, check your punctuation, check tenses of verbs and matching nouns, check to see if you have connecting words, check to see if you have a variety of sentence types, if you have time look up the spelling of the words you aren't sure about in the rest of the exam to see if you can find the correct spelling, if you have time, think about other words to add variety to your vocabulary.
You can examine many examples and find the common thread to show them, but it is more difficult for the students to see this because they are usually concentrating on vocabulary and trying to understand the piece.
When they say that the students should use their own experience as examples, they mean it.
You could take the course to become a marker and then you would have an inside track on how to teach.
But in the end, it is the students who are good at English because they have prepared everything, read widely in all subjects and current issues and really know their English who do well on the exam. So you can also just give a really good English course that covers everything you can think of and do the same job.